Canine leptospirosis (“Lepto”) is an infection caused by various species of Leptospira bacteria. It is commonly picked up from bacteria in water or soil contaminated with infected urine.

1. Referral

Monty, a 9 year old male neutered American Bulldog, presented to VCA Animal Specialty Group Emergency and Critical Care service for evaluation of anorexia, lethargy, and vomiting. A decrease in appetite with progressive lethargy was noted in both Monty and his housemate Elsa approximately 4 days prior to presentation. The day of presentation a pile of green vomitus was found in their beds. Both dogs had outdoor access to a fenced yard containing a pond and were up to date on all core vaccinations. No medications were being administered at that time.

Examination

On physical examination Monty was quiet and responsive with marked episcleritis and enophthalmos bilaterally. His abdomen was soft and non-painful on palpation and a small amount of hematechezia was retrieved on rectal. His blood pressure was on the high end of normal (176 mmHg) and his mucous membranes were slightly tacky. The remainder of his vital parameters and examination were within normal limits.

Procedures

IV fluid therapy in addition to gastroprotectants, antinausea medication, and antibiotics were started prior to abdominal ultrasound. A urinary catheter was then placed to closely regulate Monty’s urine output in addition to regular weight checks. Abdominal ultrasound revealed bilateral mild dilation of the renal pelvis’ and a small amount of peri-renal fluid. These findings were suggestive of acute nephritis, suspect either toxic insult or infectious disease process.

Diagnosis

Urine culture as well as a leptospirosis PCR urine and serum panel were submitted. The urine culture was negative while the PCR panel was urine positive for leptospirosis.

Treatment

Recheck renal values and continued IV fluid diuresis during Monty’s hospitalization revealed improving azotemia. After 5 days of hospitalization and supportive care, Monty’s renal values plateaued (BUN 44, Creatinine 3.3) and he was sent home on doxycycline and cerenia. Unfortunately, Monty’s housemate, Elsa, who was also leptospirosis positive, remained azotemic and did not respond to fluid or antibiotic therapy. Although diuresis was discussed, ultimately Elsa was humanely euthanized.

Discussion

Leptospirosis is a worldwide zoonotic disease comprised of over 250 recognized serovars (“strains”) of the spirochete leptospira. Each serovar is maintained subclinically by infected wild and domestic mammalians. Although there are saprophytic (non-pathogenic) species, at least 10 recognized serogroups are of clinical import to dogs, cats, and humans. This includes Bratislava, Autumnalis, Icterohaemorrhagiae, Pomona, Canicola, Grippotyphosa, and Batavia. Raccoons, rats, and cattle are the most common primary reservoir hosts in North America. Dogs are the maintenance host for Canicola species and can shed viable organisms intermittently for days to months after initial infection. Although both dogs and cats seroconvert after exposure to leptospirosis, cats are clinically less susceptible to infection than dogs.

The disease causing serovars vary with geographic region and reservoir species. Areas with higher rainfall or flooding that are more temperate in nature tend to have higher incidences of infection. Seasonally, more cases of leptospirosis are reported in late summer and fall. Direct infection occurs through contact with infected urine, venereal/placental transfer, ingestion of infected tissues, or bite wounds. Indirect infection can occur through exposure to contaminated water, soil or food sources. In the urban setting, exposure to stagnant water or infected rodents is believed to be the primary source of disease in dogs. Once outside of the host species, the spirochete does not replicate and can be killed by freezing, dehydration, and exposure to ultraviolet radiation.

Leptospirosis becomes pathogenic once it invades the mouth, nose, eyes, or compromised skin of a susceptible mammalian species. It multiplies rapidly in the vasculature then spreads preferentially to the kidneys, liver, spleen, nervous system, eyes, and genital tract. The kidneys are often most severely affected because the spirochete replicates and persists in the renal tubules. Clinical symptoms include fever, muscle tenderness, increased thirst and urination, vomiting, anorexia, jaundice, and painful inflammation within the eyes. Bloodwork often shows thrombocytopenia, leukopenia, and azotemia with or without elevated total bilirubin and ALT. In dogs, canicola and icteroheaemorrhagiae are most predominately associated with renal failure, coagulopathies, and hepatic disease. If standing water is present and the circumstances are favorable for spirochete persistence, Leptospirosis should be a differential for acute rises in renal or hepatic values.

Diagnosis of leptospirosis involves microscopic agglutination testing (MAT) with titers and dark-field microscopy. A four-fold increase or decrease in MAT titer is indicative of an active leptospirosis infection. MAT must be paired with titers otherwise the test cannot distinguish between natural infection and vaccination. Dark field microscopy of the urine, PCR, and bacterial culture/isolation are specific to leptospirosis but not sensitive.

The cornerstone of treatment includes supportive therapy correlated to clinical signs. IV fluid diuresis, antiemetics, careful monitoring of ins and outs with placement of a urinary catheter, and/or blood transfusions may be required. Antibacterial therapy with penicillins (which terminate leptospiremia) or doxycycline (which causes rapid elimination from the kidneys) should be initiated immediately after diagnosis. In cases non-responsive to fluid therapy, dialysis should be strongly considered. With aggressive treatment, recovery from infection is possible and eventually the leptospire organism will be eliminated from the body. Unfortunately, pathologic changes that occur during the course of infection will persist in affected tissues past the point of clinical recovery.

Control of environmental conditions and reducing exposure to infected animals is the cornerstone of prevention. Immunization with leptospirosis vaccines targeting canicola, icterohaemorrhagiae, grippotyphosa, and pomona, are effective at reducing the severity and prevalence of canine leptospirosis. If an animal is able to mount an appropriate antibody load to the infecting species, they may be able to clear the infection without apparent clinical signs.

Recovery

At his last recheck, Monty’s kidney values had improved significantly (BUN 14, Creatinine 1.8), he remains antibody positive for multiple leptospirosis serovars. Although not as prevalent as in other parts of the country due to dry weather conditions, leptospirosis should be on clinician’s radars even in Southern California and especially where standing water is present.

Besides his professional interest in surgery and emergency medicine, Dr. Andreas Andreou also has a passion for avian and exotic medicine. In 2004, he was honored with the Pamela Slack Award, which is presented to the third-year veterinary student who has demonstrated the most outstanding competence and motivation in avian medicine.